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We introduce a novel metric space search data structure called EGNAT, which is fully dynamic and designed for secondary memory. The EGNAT is based on Brin's GNAT static index, and partitions the space according to hyperplanes. The EGNAT implements deletions using a novel technique dubbed Ghost Hyperplanes, which is of independent interest for other metric space indexes. We show experimentally that...
Metric space searching is an emerging technique to address the problem of efficient similarity searching in many applications, including multimedia databases and other repositories handling complex objects. Although promising, the metric space approach is still immature in several aspects that are well established in traditional databases. In particular, most indexing schemes are not dynamic, that...
It has been a long way since the beginnings of metric space searching, where people coming from algorithmics tried to apply their background to this new paradigm, obtaining variable, but especially difficult to explain, success or lack of it. Since then, some has been learned about the specifics of the problem, in particular regarding key aspects such as the intrinsic dimensionality, that were not...
An important trend for e-commerce sites is to be able to provide a personalized experience for the consumer, and there has been an increasing research interest in Web usage mining techniques to that end. One of the current problems of Web usage mining deals with privacy and anonymity. The data it uses, contains sensitive information that should be protected. We introduce the microaggregation of Web...
We present novel query algorithms that efficiently support some popular XPath operations over LZCS-transformed documents. The LZCS transformation compresses a redundant XML collection without loss. The main idea of LZCS, inspired by Lempel-Ziv compression, is to replace whole substructures by previous occurrences thereof, and our algorithms try to reuse the work done over those repeating substructures...
This paper describes aspects of the power electronics control of wave energy conversion. The objective of the power converter is to drive a switched reluctance linear machine which works as direct-drive power take off (DDPTO) system for a point absorber. FEM analysis and simulations of the electrical machine were taken into account in the design of the converter control strategy. Finally, laboratory...
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